Dr. Vedantham and others who study deep vein thrombosis say a major problem is how often it’s misdiagnosed. Vedantham said that’s not an indictment. Front-line general practitioners see hundreds of simple cases, and only a tiny fraction turn out to be more complicated than the initial diagnosis. “Sometimes it’s hard to tell a small thing is a big thing,” he said.

Still, that’s why patients need to be their own advocates, Vedantham said. “When people come in with one leg hurting and swelling, (physicians) should at least think about a blood clot as a possibility,” he said. “Even a low-level of suspicion, you should get an ultrasound at least.”

Also, it’s essential to check risk factors such as a history of cancer, hormonal changes including birth control pills and a family history. Considering 350,000 to 600,000 people a year develop deep vein thrombosis and related conditions, it’s worth being aware, he said.

Vedantham’s interest in the condition peaked in 2008-09 after the U.S. surgeon general called for a major push to prevent it because of the rate of fatalities. The National Institutes of Health soon afterward funded Vedantham’s study.

Stagoski will get regular checkups because people who have had clots are at risk of getting them again. However, she says the surgery fixed her condition. “I don’t have swelling or pain; no compression stocking; life back to normal,” she said.